Boxer primers are a self contained priming system. The priming compound and anvil all in one piece that only requires the correct size primer pocket and a flash hole through the cartridge to function.
Berdan primers do not have the anvil in them, they are just the priming compound. The anvil is made into what would be the center of the flash hole of a normal brass or steel case with several smaller flash holes around the perimeter of the anvil. This is why it is difficult to remove and replace the primers. Where a normal decapping pin would pass through there is actual casing material.
You can convert berdan brass to boxer but as explained before this is a project of diminishing returns unless the brass is something you really don't want to let go of. There is a
Youtube video of a guy converting steel cased Wolf into boxer primers.
While the idea is ridiculous to me and he is a little off on his info you can see the difference in the primers clearly in the video. I think watching it will highlight for you just how pointless and labor intensive the project would be.